A comprehensive redesign by Printed Motor Works of its low profile, high power density wheel motor, developed for Ocado's warehouse robots, has delivered a boost to its capabilities. Improvements to the design of the motor have increased the axial load strength by up to 650% despite being no heavier - and all within the same space envelope and a maximum depth of less than 50mm
PMW says that its new XR15-05e in-wheel motor has also been made more durable, with stronger cable strain relief and an enhanced rotor-to- body seal. Deep groove ball bearings have been replaced with an angular contact bearing unit to better withstand offset axial loads. Finite element analysis was used to verify the design improvements, and PMW states that endurance limit analysis has indicated a much extended product life.
In addition, the component count has been reduced by 30%, simplifying assembly for volume manufacture and reducing overall product cost. Electromagnetic active components have been upgraded, preventing a reduction in performance as battery voltage drops. Encoder performance has also been improved, the optical encoder being replaced by an on-axis magnetic type, said to offer greater tolerance to contamination with nearly double the resolution: with lower cost and no impact on the overall package.
The improvements were made possible by Printed Motor Works' experience and expertise in the serial production of the original drive motors for Ocado's warehouse robots, the workhorses of their Ocado Smart Platform (OSP). Rather than having a conventional layout with aisles between rows of racks, Ocado's warehouse system consists of a large three-dimensional mesh of cells accessed from above by swarms of cuboid robots, each equipped with eight in-wheel motors.
PMW cites other possible applications for these upgraded in-wheel motors as including industrial robots and AGVs, warehouse shuttle drives, personal mobility devices and directly driven turntables or mounts for radar, lidar and cameras.
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